Обучающая программа построения параллелограмма по двум сторонам и диагонали

var
  Form1: TForm1;
  a,i: Integer;
  x,y: Integer;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.SpinEdit1Change(Sender: TObject);
begin
 i:=0; 
 BitBtn1.Enabled:=False; 
 BitBtn2.Enabled:=True;
end;
 
procedure Proizvol_Otrezok;
begin
a:=Form1.SpinEdit1.Value;
a:=10*a;
x:=240; y:=280;
Form1.Image1.Canvas.pen.Width:=3;
Form1.Image1.Canvas.pen.Style:=psSolid;
Form1.Image1.Canvas.Brush.Color:=clWhite;
Form1.Image1.Canvas.Rectangle(0,0,Form1.Image1.Width,Form1.Image1.Height);
Form1.Image1.Canvas.MoveTo(x-a,y);
Form1.Image1.Canvas.LineTo(x+a,y);
Form1.Image1.Canvas.Font.Size:=14;
Form1.Image1.Canvas.TextOut(x-a-15,y+2,'A');
 
Form1.Image1.Canvas.MoveTo(x-a-50,y);
Form1.Image1.Canvas.LineTo(x+a+50,y);
Form1.Image1.Canvas.TextOut(x+a+53,y+2,'L');
Form1.Image1.Canvas.Pen.Style:=psSolid;
Form1.Image1.Canvas.Brush.Color:=clBlack;
Form1.Image1.Canvas.Ellipse(x-a-15,y+a-1,x-a-10,y+a+1);
Form1.Image1.Canvas.Brush.Color:=clWhite;
 
 
Form1.Memo1.Text:='Для начала проведем произвольную линию L. Поставим на прямую точку А.';
end;
 
procedure Tochka_A;
begin
Form1.Image1.Canvas.pen.Width:=1;
Form1.Image1.Canvas.pen.Style:=psDot;
Form1.Image1.Canvas.Arc(round(x-a), round(y-a),
round(x+a),round(y+a),round(x-a),round(y+4*a/3),
round(x-a),round(y-4*a/3));
Form1.Image1.Canvas.TextOut(x+a+3,y+2,'D');
Form1.Memo1.Text:=' '
+IntToStr(Form1.SpinEdit3.Value)+'см'; ;
end;
 
 
procedure TForm1.BitBtn2Click(Sender: TObject);
begin
i:=i+1;
Case i of
1: Proizvol_Otrezok;
2: Tochka_A;
end;
BitBtn1.Enabled:=True;
 
end;
 
procedure TForm1.Button1Click(Sender: TObject);
begin
Close;
end;
 
end.

procedure Zasechka_2;
begin
b:=Form1.SpinEdit2.Value;
b:=10*b;
ax:=x-a; ay:=y;
Form1.Image1.Canvas.Brush.Color:=clWhite;
Form1.Image1.Canvas.pen.Width:=1;
Form1.Image1.Canvas.pen.Style:=psDot;
Form1.Image1.Canvas.Arc(round(ax-b), round(ay-b),
round(ax+b),round(ay-b),round(ax+b),round(ay),
round(ax+b),round(ay));
end;